Efficient ventilation of rooms, such as living space or office space, is becoming increasingly important in connection with energy-saving measures. Air exchange with outside air can be achieved by opening a window, but when the heating or air-conditioning is switched on, a large amount of thermal energy escapes through the window, or warm air flows into the cooled interior of the building. A substantial proportion of the energy used for heating or cooling is lost as a result. Furthermore, an open window is always associated with a greater risk of burglary.
For these reasons, systems have already been developed with which heat can be recovered decentrally when ventilating a room. In this context, “decentrally” means independently of any heating or cooling system that is installed. However, common systems require much space and project into the room, due to the heat storage units that are needed. Extensive construction measures are also necessary in order to install such systems.